'Embarrassing' mishap causes New Zealand PM to take commercial flight to Japan

The New Zealand defence force plane flying the country's prime minister suffered an "embarrassing" mishap after it broke down on the way to Japan.

A New Zealand Air Force plane sits on the tarmac at Auckland Airport. File pic: AP

Christopher Luxon was forced to take a commercial flight from Papua New Guinea after the Boeing 757 broke down during a refuelling stop.

The rest of the delegation, which reportedly included trade minister Todd McClay, dozens of business leaders and journalists were left stranded in the capital, Port Moresby.

Air New Zealand chief executive Greg Foran, who was one of the stranded 52 business leaders and reporters, decided to divert an Auckland to Tokyo flight via Brisbane to pick everyone up, Sky News Australia reported.

A "fuse issue" was reported as the cause of the problem and meant the plane - also known as "old Betty" - could only fly short distances.

The New Zealand leader is expected to spend four days in Japan where he will meet with Prime Minister Fumio Kishida and promote business in his country.

The defence force's two 757s are more than 30 years old, making them increasingly unreliable.

Defence minister Judith Collins told radio station Newstalk ZB on Monday the consistent flight issues were "embarrassing" and the ministry was looking at flying Mr Luxon and his delegation commercially from now on.

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Back in March, a technical hitch to the aircraft landing gear system meant Mr Luxon was forced to take a commercial flight to attend an ASEAN summit in Melbourne.

New Zealand's defence force is struggling with ageing equipment and retaining sufficient personnel.

The government has said it would like to spend more on defence but is also trying to reduce spending as the country faces economic headwinds.